Now I want to build a SAW filter between the coax cable and the dongle. So I need a DC bypass for the SAW filter. Does anyone know how to build a circuit with a SAW filter and a DC bypass?

Viele Grüße
Konstantin

Have a look for bias-t circuits, basically you need one on each side of the saw filter (one to extract the DC and block the power from the SAW and one on the other side of the SAW to re-inject it) or one on the amplifier side and feed the DC in there .

I have following setup for receiving Flarm signals (868.3MHz):
Antenna -> amplifier -> 10m coax cable -> dongle from rtl-sdr.com with bias tee -> Raspberry
Now I want to build a SAW filter between the coax cable and the dongle. So I need a DC bypass for the SAW filter. Does anyone know how to build a circuit with a SAW filter and a DC bypass?

It's probably better to put the filter between antenna and amplifier, where it should be...

There have been some designs posted in the best antenna thread, I think abcd567 has previously posted a basic design, any bias-t should block RF from the DC path, that is one of the basic functions of it as it would not work otherwise, they are simple devices consisting of a capacitor between the RF input and output to let the RF pass and an inductor in the DC line to block RF from the DC path, nothing more, nothing less.image.jpeg

.........any bias-t should block RF from the DC path, that is one of the basic functions of it as it would not work otherwise, they are simple devices consisting of a capacitor between the RF input and output to let the RF pass and an inductor in the DC line to block RF from the DC path, nothing more, nothing less.image.jpeg